Visualization of a stent implanted in a coronary artery is made difficult because images produced by X-ray imaging may be of insufficient quality to resolve the fine structure of an implanted stent in a single image. In order to improve image quality, known systems register a series of image frames containing landmarks that are stationary with respect to a stent and average them together. As the number of frames being registered increases, the image quality improves. An increase in the number of frames also requires an increase in the computational time and memory resources to complete a calculation, potentially beyond what is permissible within a system. Also some frames obtained in the presence of substantial cardiac motion use additional processing resources and may reduce the clarity of stent visualization. A system according to invention principles addresses these deficiencies and related problems.